<form id="form1" name="formulariologin" method="post" action="index.php?security_administrator=login">
    <?php
    if (empty($_SESSION["authenticated_id_user"]) && $security_in == 1) {
        ?>
        <p class="error">Datos de ingreso incorrectos.</p>
    <?php } ?>                        
    <p>
        <label><strong>Usuario:</strong>
            <input type="text" name="user" class="inputText" id="textfield" onkeypress="iSubmitEnter(event, document.formulariologin);" />
        </label>
    </p>
    <p>
        <label><strong>Contrase&ntilde;a:</strong>
            <input type="password" name="password" class="inputText" id="textfield2" onkeypress="iSubmitEnter(event, document.formulariologin);" />
        </label>
    </p>
    <a class="black_button" href="#" onclick="document.formulariologin.submit();"><span>Ingresar</span></a>      
</form>